Electrophotographic copier of image transfer type

ABSTRACT

An image transfer type electrostatic copier includes a rectangular box open at one end and connected to a suction fan at its other end and has a pair of longitudinally spaced slits formed in a wide wall thereof which is separated by a removable wall section. A cleaner belt extends from a storage roll through one slit along the inside face of the box wall through the other slit to a take-up roll. A photosensitive web is sucked into the box and traverses a looped path which extends along the cleaner belt under the influence of the reduced pressure in the box. The web, is driven and charged, exposed to a scanned image, has toner applied and the toned image is transferred to copy paper.

nite Tanaka et al. Aug. 6, 1974 [54] ELECTROPHOTOGRAPHIC comm or 3,598,488 8/1971 DiFrancesco ..355/1.s x IMAGE TRANSFER TYPE 3,667,840 6/1972 Engel et al. 355/3 R [75] Inventors: Susumu Tanaka, Sakai; Yuji Enoguchi, l-ligashi-Osaka; Takao Primary ExaminerR1chard M. Sheer Fujiwara, Sakai, all of Japan Attorney, Agent, or Firm-Wolder & Gross [73] Assignee: Minolta Camera Kabushiki Kaisha,

' osakarjapan 57 ABSTRACT [22] Filed: Mar. 7, 1973 An image transfer type electrostatic copier includes a pp 338,782 rectangular box open at one end and connected to a suction fan at its other end and has a pair of longitudi- 30] Foreign Application Priority Data nally spaced slits formed in a wide wall thereof which M l 6 1972 J 47 31636 is separated by a removable wall section. A cleaner apan belt extends from a storage roll through one slit along the inside face of the box wall through the other slit to [52] US. Cl 355/l555355/51/13335553486 a takeup re A photosensitive web is Sucked into the 51 l t Cl 15/00 box and traverses a looped path which extends along d 8 5 16 the cleaner belt under the influence of the reduced 1 1e earc pressure in the box. The web, is driven and charged, References Cited exposed to a scanned image, has toner applied and the UNITED STATES PATENTS Stoever et al 355/15 X toned image is transferred to copy paper.

9 Claims, 4 Drawing Figures ELECTROPIIOTOGRAPI-IIC COPIER OF IMAGE TRANSFER TYPE BACKGROUND OF THE INVENTION The present invention relates to electrophotographic copiers of the image transfer type, more particularly to an apparatus for use in electrophotographic copiers of the powder image transfer type including a photosensitive element in the form of a flexible sheet for effectively removing a powdered toner from the photosensitive surface of the element which toner remains thereon aftera powder image has been transferred to copy paper.

Typical of cleaning apparatuses heretofore used in electrophotographic copiers of the powder image transfer type are those in which one or a plurality of rotary brushes are provided for the photosensitive element in sliding contact with its surface to remove the residual toner from the surface, as disclosed in the pulications of Japanese Pat. application No. 40-12831/1965, No. 41-14069/1966, No.

42-16590/1967, etc., those in which the toner is blown away with an air stream as disclosed in the Publication of Japanese Pat. application No. 43-14520/1968, and those of a construction in which the residual toner on the photosensitive surface is removed by rotary brush and the'toner caught on the brush is then blown off by an air stream as disclosed in the publication of Japanese Pat. application No. 42-16600/1967. With these apparatuses, however, it is difficult to achieve a sufficient cleaning effect inasmuch as the cleaner means, such as rotary brush or air stream, contacts the photosensitive surface over a small limited area. Moreover, they are expensive.

Another type of apparatus is already known as described in the publication of Japanese Pat. application No. 41-7195/1966 which comprises a roll of cleaning web adapted for sliding contact with the surface of a drum-shaped photosensitive element such that the web is progressively wound up on a take-up roll in operative relation to the operation of the machine so as to clean the photosensitive surface with a fresh surface section of the web. However, since the apparatus is of such construction that the web is pressed against the photosensitive surface mechanically under a constant pressure, it is not adapted to clean a photosensitive element which is driven in the form of a belt, it being very difficult to keep the pressure constant in the case of the belt-type photosensitive element. In addition, the apparatus has the drawback of being extremely complex.

SUMMARY OF THE INVENTION An object of this invention is to provide an apparatus comprising a cleaning belt adapted for sliding contact, over a sufficiently wide area, with a photosensitive element which is driven in the form of a belt to thereby achieve a greatly improved cleaning effect.

Another object of this invention is to provide an apparatus which is extremely simple in construction and is therefore very inexpensive and which permits easy replacement of a cleaning belt.

Still another object of this invention is to minimize the contact pressure for causing the cleaning belt to slide on the surface of the photosensitive element and to thereby prevent the photosensitive surface from deterioration due to the frictional sliding movement of the cleaning belt on the photosensitive surface.

To fulfill the above objects, the apparatus of this invention includes a suction box by which a looped portion of a photosensitive element, driven in the form of a belt, is sucked into the interior of the box in sliding contact with its inner wall faces, whereby the photosensitive element is held in a planar shape as required for charging and exposure, under a tension required for development and image transfer.

The apparatus further includes a cleaning belt adapted to clean the surface of the photosensitive element and removably mounted in the suction box, the cleaning face of the belt being exposed to the interior of the box along its inner wall face to come into sliding contact, over a sufficient area, with the surface of the photosensitive element drawn into the suction box for the removal of a residual toner on the photosensitive surface.

The cleaning belt provided in the suction box has opposite ends extending outward from the box through suitable slits formed therein, one end being wound up on a stock roll with the other end secured to a take-up roll so that an old section will be would up bya manual or automatic winding operation to place a fresh section of the cleaning face into the suction box.

Because of the construction in which almost the entire area of one inner wall face of the suction box can be utilized to provide the cleaning belt with its cleaning face exposed to the interior of the box, the area of the cleaning face for sliding contact with the photosensitive surface can be increased remarkably as compared with the contact area conventionally available for cleaning to assure a materially improved cleaning efficiency.

The contact pressure of the cleaning belt on the photosensitive element is given by a very small suction exerted on the element by the suction box, so that the contact pressure which is therefore very low will not produce a great friction which would otherwise result from high pressure contact of the belt with the photosensitive element.

The suction box per se is simply in the form of a rectangular box, this serving to greatly simplify the construction for mounting the cleaning belt in place and for removing the same for replacement to render the apparatus inexpensive to manufacture.

Other objects and advantages of this invention will become more apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing the construction of principal part of an embodiment of this invention;

FIG. 2 is a sectional view showing only part of another embodiment;

FIG. 3 is a sectional view showing the construction of principal part of another embodiment; and

FIG. 4 is a sectional view showing only part of another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, a document D is placed face down on a document table 1 made of a transparent glass plate or the like. An illuminating system 2 and an image-forming optical system 3 are disposed below the document table I. As illustrated in detail, for example in the publication of Japanese Pat. application No. 39-6647/ i964, the illuminating system 2 comprises first movable means adapted to travel at a velocity of v from the solid line position to the broken line position in the drawing and including a lamp L and mirror M1, and second movable means likewise adapted to travel at a velocity of v/2 from the solid line position to the broken line position and including mirrors M2 and M3. The light path extending from the document surface to an image-forming lens 3a is so designed as to have a constant length all the time during a copying operation in spite of the travel of both the movable means.

The image-forming optical system 3 is stationary and comprises the image-forming lens 3a and the mirrors M4. The reflected light from the surface of the document illuminated by the lamp L is led onto a photosensitive element P by means of the mirrors M1, M2, M3 and M4 and lens 3a to form an image on the element P for exposure.

The photosensitive element P made of a flexible sheet is in the form of a belt and is supported on a drive roller 6 to be driven by a feed roller 5. ln synchronism with the advance of the illuminating system 2, i.e., with an operation to illuminate the surface of the document, the photosensitive element P is driven at the same velocity v as the first movable means L and M1 in the direction indicated by an arrow'in the drawing, whereby the element is subjected to the above-mentioned exposure.

Disposed along the path of advance of the photosensitive element P are a charging unit 7 for charging the photosensitive surface prior to the exposure, a developing unit 8 for visualizing an electrostatic latent image corresponding to the image of the document and formed on the photosensitive surface by the exposure,

and a transfer unit 9 for transferring the visual powder image on the photosensitive element to copy paper T. These units are well-known for use in copiers of the type described. The developing unit 8 includes means for applying a powdered toner to the photosensitive surface to develop the latent image. Due to the charge given to the toner, the toner is electrostatically attracted to and deposited on the latent image bearing surface to render the latent image visual. The transfer unit 9 brings the copy paper T into intimate contact with the surface of the photosensitive element P bearing thereon the visual powder image to transfer the image to the copy paper T.

As illustrated, the copy paper T in the form of a roll is accommodated in a copier. The leader end of the paper is paid out at a rate equal to the speed of the photosensitive element P in timed relation to the movement of the element P and is cut to a predetermined size by a cutter 10. A guide roller 11 for the photosensitive element P is disposed at the transfer station. Guide rollers for feeding the paper T are indicated at 12.

The copy paper T bearing the powder image transferred thereto is separated from the photosensitive element P and conveyed by a fixing belt 13. During the transport, the power image is fixed by a fixing unit 14 and the paper is then sent out from the machine.

Although an electrophotographic copier of the powder image transfer type has been briefly described with respect to the well-Known steps of charging, exposure, development and transfer operations thereof, the constructions of the respective units, being well known, will not be described in detail.

It will be seen from the drawing that the photosensitive element P is in the form of belt, an unused fresh photosensitive portion of which is stored in a stock roller 15 in the form ofa roll (not shown). An old portion thereof with fatigued photosensitive face is wound up on a take-up roller 16. The portion intervening between the rollers 15 and 16 is repeatedly moved back and forth for the copying operation. When this portion becomes fatigued, a fresh portion will be paid out from the stock roller 15, and the deteriorated portion will be wound up on the take-up roller 16. This operation is conducted by a suitable automatically or manually operative member.

For a copying operation, the photosensitive element P is simply driven reciprocally. Normally, therefore, both the rollers 15 and 16 are locked against rotation during the copying operation. The photosensitive element P driven by the drive roller 6 advances from the solid line position to the broken line position in the drawing to perform the copying operation. Simultaneously with the return movement of the illuminating system 2, the feed roller 5 is driven reversely, causing the drive roller 6 to drive the photosensitive element P backward from the broken line position to the solid line position. Consequently, the photosensitive element P is looped as indicated at P' and P" as shown during its reciprocal movement.

The looped portions P and P" are drawn into the suction box 17 along its inner wall faces under vacuum suction acting in compartments 17a and 17b of the suction box 17, the photosensitive element P thus being guided by the suction box 17 for reciprocal movement.

The suction box 17 supports the stock roller 15 and the take-up roller 16 at the inlets of the compartments 17a and 17b, respectively. Normally, both the rollers 15 and 16 are locked against rotation but are rendered rotatable as desired, as when the element P is wound up. Disposed in the rear of the suction box 17 is an exhaust fan 18, serving as a source of the vacuum suction, which exhausts air from the compartments 17a and 17b to suck the looped portion P into the compartment 17a and the looped portion P into the compartment 17b. Behind the exhaust fan 18 there is a duct 19 for collecting the toner and dust removed off the photosensitive surface. According to the embodiment of FIG. 1, a passage 1712' between the compartment 17b and the exhaust fan 18 is smaller than a passage 17a between the compartment 17a and the exhaust fan 18 to promote the return of the photosensitive element P by the suction of the compartment 17a. With this construction, it is further possible to release the feed roller 5 from the drive roller 6 to render the roller 6 free to rotate during the return of the photosensitive element P so that the photosensitive element P will be returned automatically under the suction of the compartment 17a without the necessity to drive the feed roller 5 in the reverse direction.

The cleaning belt 20 is disposed in the suction box 17, with its cleaning face positioned along the inner wall face of the compartment 17b.

A cleaning belt 20 is inserted into the compartment 17b by being passed over and along an inner wall face of the compartment on which the photosensitive face of the element P moves in sliding fashion. The cleaning belt 20 comprises, for example, a flexible belt made of a polyester film (e.g., Mylar, trademark of E.

I. du Pont de Nmours and Co., Lumirror, trademark of Toray Industries Inc., Japan, etc.) or the like and a fur, artificial fur or vegetable fibers adhered to the surface of the belt.

The cleaning belt is inserted into the compartment 17b through slits 21 and 22 formed in the wall of the suction box 17 or may otherwise be removably inserted into the box in a suitable manner. The belt is positioned along the inner wall face 17c and is wound on a stock roll 23 at its one end and on a take-up roll 24 at the other end thereof. When the portion positioned over the inner wall face 170 has been soiled and deteriorated, the soiled portion is wound up on the take-up roll 24 by suitable means to pull out a fresh portion from the stock roll 23 and place the same over the inner wall face 170.

When the photosensitive element P moves reciprocally for the copying operation, the photosensitive surface is cleaned by the cleaning belt 20 in sliding contact therewith, whereby the residual toner on the photosensitive surface is removed therefrom and transferred onto the cleaning belt 20. The toner is then drawn by the exhaust fan 18 and collected in the dust collecting duct 19. If a portion 25 of the suction box 17 between the slits 21 and 22 is adapted to be opened and closed, for example, inthe manner of a lid to insert the cleaning belt 20 into the suction box 17, the belt 20 will be handled with ease for placement, removal and replacement.

FIG. 2 shows an embodiment in which a stock roller accommodating a fresh photosensitive element serves also as a drive roller. The roller 35 winds up an operative portion of the photosensitive element P on its' outer periphery to move the photosensitive element P forward in synchronism with the exposure making operation of the illuminating system (see FIG. 1). When the roller 35 is driven in the reverse direction, a looped portion P of the element P is sucked into a suction box 37. A cleaning belt 20 disposed along the upper inner wall face 37c of the box 37 cleans the photosensitive surface when the element is drawn into the box. Accordingly, the suction box 37 in this embodiment includes only one compartment. A take-up roller 36 for the photosensitive element P is supported at the inlet of the suction box 37 in the same manner as in FIG. 1. The cleaning belt 20 is inserted through slits 38 and 39 into the suction box 37, with its stock roll 23 and take-up roll 24 supported outside the suction box 37 by unillustrated means. A portion 40 between the slits 37 and 38 can be opened as above.

FIG. 3 shows an embodiment including a photosensitive element PEL in the form of an endless belt which is driven in one direction by a drive roller 6 rotatable in the direction of an arrow. As in the case of FIG. 2, the photosensitive surface of the element is cleaned by a cleaning belt 20 disposed along the upper inner wall face 47c of the suction box 47. As in FIG. 2, the cleaning belt 20 is inserted into the suction box 47 through slits 48 and 49 therein. A stock roll 23 and a take-up roll 24 are supported by unillustrated means outside the box 47. A portion 50 between the slits 48 and 49 is adapted for opening. The photosensitive element PEL is of course driven in synchronism with the exposure making operation of an illuminating system 2 at a velocity equal to that of the first movable means thereof.

FIG. 4 shows an embodiment in which the looped portion P of a photosensitive element PEL in the form of an endless belt as shown in FIG. 3 is passed around and supported on a roller 61 rotatably supported in a suction box 57 and a drive roller 7 drives the photosensitive element PEL. In this case, a cleaning belt 20 is disposed along a lower inner wall face 570 of the suction box 57. Slits 58 and 59 are formed to insert the cleaning belt 20 into the box. A portion 60 is adapted for opening.

In FIGS. 2, 3 and 4, the same parts as those of FIG. 1 are referred to by the same reference numbers and characters.

It will be apparent from the foregoing description that in the foregoing embodiments, the area of contact between the photosensitive element P or PEL and the cleaning belt 20 can be provided as desired on the inner wall face of the suction box 17, 37, 47 or 57. The resulting cleaning effect improves with the increase in the contact area, and there is no need to increase the pressure of contact therebetween. The contact pressure acting between the contact surfaces is determined by the pressure reducing ability of the suction box, namely by the exhausting ability of the suction source, i.e., the exhaust fan 18. The loop can be formed with a very small exhausting force. This serves to reduce the pressure for the contact between the photosensitive element and the cleaning belt and assures uniform contact to mitigate friction on the photosensitive surface.

What is claimed is:

1. An electrostatic copier of the image transfer type comprising a longitudinally extending suction box having an opening proximate one end thereof and a pair of longitudinally extending walls having internal faces, a cleaning belt including a section extending along one of said box internal faces and being removable therefrom, an elongated web having a photosensitive surface and traversing a loop path extending into said box and including a first longitudinal run along said cleaning belt and a second longitudinal run along the opposite internal face of said box and an end run joining the ends of said longitudinal runs within said box, suction means connected to the interior of said box remote from said opening for reducing the pressure within said box and for sucking a portion of said web into said box drive means for driving at least a portion of said web along the length thereof to travel through said box end opening, means for producing an image on said web photosensitive face during the movement of said web and means for transferring said image from said web to an image receiving substrate.

2. The copier of claim 1 wherein one of said box walls has a pair of longitudinally spaced transverse slots formed therein, said cleaning belt extending through one of said slots into said box, along the internal face of said wall to the other slot and then outwardly through said other slot.

3. The copier of claim 2 wherein the portion of said wall between said slots is removable.

4. The copier of claim 2, including a belt take-up roll and a belt storage roll supported externally of said box, said cleaning belt extending between said rolls through said slots.

5. The copier of claim 1 wherein said image producing means comprises means for electrically charging said belt photosensitive surface, optical scanning means for projecting a light image of an original on said charged surface during the movement of said belt to produce a latent image and means for applying a toner powder to said latent image to produce a powder image.

6. The copier of claim 1 including a longitudinal partition dividing said suction box into first and second longitudinally extending compartments having openings at an end of said box remote from said suction means, said drive means including a drive roll longitudinally spaced from said end openings externally of said box, first means for retaining one end of said web proximate one of said end openings, second means for retaining the opposite end of said web proximate the other end of said end openings, said web traversing a looped path from said first retaining means in a first compartment then about said drive roller and a second looped path in the other compartment and to said sec- 0nd retaining means.

7. The copier of claim 1 wherein said drive means includes a drive roll located externally of said box and longitudinally spaced from said box end opening, one end of said web being engaged and driven by said drive roll and means for retaining the other end of said web proximate said end opening.

8. The copier of claim 1 wherein said drive means includes a drive roll located externally of said box and longitudinally spaced from said box end opening and said web comprises an endless belt extending around said drive roll and projecting into said suction box through said end opening.

9. The copier of claim 8 including a roll rotatably supported within said box, said extending about said roll within said box. 

1. An electrostatic copier of the image transfer type comprising a longitudinally extenDing suction box having an opening proximate one end thereof and a pair of longitudinally extending walls having internal faces, a cleaning belt including a section extending along one of said box internal faces and being removable therefrom, an elongated web having a photosensitive surface and traversing a loop path extending into said box and including a first longitudinal run along said cleaning belt and a second longitudinal run along the opposite internal face of said box and an end run joining the ends of said longitudinal runs within said box, suction means connected to the interior of said box remote from said opening for reducing the pressure within said box and for sucking a portion of said web into said box drive means for driving at least a portion of said web along the length thereof to travel through said box end opening, means for producing an image on said web photosensitive face during the movement of said web and means for transferring said image from said web to an image receiving substrate.
 2. The copier of claim 1 wherein one of said box walls has a pair of longitudinally spaced transverse slots formed therein, said cleaning belt extending through one of said slots into said box, along the internal face of said wall to the other slot and then outwardly through said other slot.
 3. The copier of claim 2 wherein the portion of said wall between said slots is removable.
 4. The copier of claim 2, including a belt take-up roll and a belt storage roll supported externally of said box, said cleaning belt extending between said rolls through said slots.
 5. The copier of claim 1 wherein said image producing means comprises means for electrically charging said belt photosensitive surface, optical scanning means for projecting a light image of an original on said charged surface during the movement of said belt to produce a latent image and means for applying a toner powder to said latent image to produce a powder image.
 6. The copier of claim 1 including a longitudinal partition dividing said suction box into first and second longitudinally extending compartments having openings at an end of said box remote from said suction means, said drive means including a drive roll longitudinally spaced from said end openings externally of said box, first means for retaining one end of said web proximate one of said end openings, second means for retaining the opposite end of said web proximate the other end of said end openings, said web traversing a looped path from said first retaining means in a first compartment then about said drive roller and a second looped path in the other compartment and to said second retaining means.
 7. The copier of claim 1 wherein said drive means includes a drive roll located externally of said box and longitudinally spaced from said box end opening, one end of said web being engaged and driven by said drive roll and means for retaining the other end of said web proximate said end opening.
 8. The copier of claim 1 wherein said drive means includes a drive roll located externally of said box and longitudinally spaced from said box end opening and said web comprises an endless belt extending around said drive roll and projecting into said suction box through said end opening.
 9. The copier of claim 8 including a roll rotatably supported within said box, said extending about said roll within said box. 